...states that it was added 14 March 2009. OpenBSD 4.5-release was tagged in CVS around ~1-2 March 2009. As jggimi has already stated, unless you are running 4.5-current, pingus has not been verified on any previous version of OpenBSD, & no one will bother doing so. You are on your own if you want to run pingus on anything older than 4.5-current.

In case there is any question, let me repeat myself: You are on your own if you want to run pingus on anything older than 4.5-current.

If you are confused by the different versions of OpenBSD: -release, -stable, & -current, study Section 5.1: